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Potatoes are a starchy type of vegetable, meaning they are full of starch carbohydrates. After a long digestive process, starches eventually convert into glucose. Potatoes also have a small amount of naturally occurring sugar, which converts to glucose in a different manner. Your system uses glucose to fuel every cell, so having a lot of carbohydrates in your diet is important.

Tip

Your body turns starchy foods such as potatoes into glucose, a simple sugar which in turn fuels your body and its cellular functions.

Sugar Function

A medium-sized, 4-ounce potato has about 2 grams of natural sugar, a type of simple carbohydrate. In your digestive tract, sugar metabolizes more quickly than any other macronutrient. Once sugar hits your small intestine, enzymes that are secreted by intestinal walls trap sugar molecules. The enzymes rapidly break down sugar into glucose, which is the smallest, simplest type of sugar. Your bloodstream picks up glucose as it absorbs through intestinal walls. Once in your bloodstream, glucose enters cells with the help of the hormone insulin.

Digestion of Starch

The same 4-ounce potato has approximately 23 grams of starch, which is a complex carb. Starch starts breaking down in your mouth. As you chew, more saliva is secreted. Saliva clings to starch and begins deconstructing these large, branched compounds. Starch converts into maltose, a smaller, simpler carbohydrate, right in your mouth. Maltose heads down to your small intestine, where it converts to glucose and is free to enter your bloodstream to fuel cells.

Glycemic Index Rating

Because potatoes are comprised of more than 92 percent carbohydrates -- in the form of sugar and starch -- they are relatively high on the glycemic-index scale. The glycemic index rates foods on a scale of 1 to 100 based on how quickly they raise your blood sugar levels. Foods closer to 100 elevate your blood sugar more quickly than foods on the lower end of the scale. Mashed potatoes and boiled white potatoes are 82 and 87 on the glycemic scale, respectively. Sweet potatoes are a little lower, having a glycemic index rating of 70, according to Harvard Medical School.

Carb Recommendation

Your diet should consist of 45 to 65 percent carbohydrates, according to the 2015 Dietary Guidelines for Americans. Both sugar and starch have 4 calories per gram, so if you follow an average 2,000-calorie diet, you'll need 225 to 325 grams of carbohydrates per day. A 4-ounce potato has nearly 25 grams of total carbohydrates. The exact amount you need depends on your activity level. If you have a physically demanding job or work out on a regular basis, you probably need the higher end of the recommendation, versus someone who is relatively sedentary and needs less.

About the Author

Melodie Anne Coffman specializes in overall wellness, with particular interests in women's health and personal defense. She holds a master's degree in food science and human nutrition and is a certified instructor through the NRA. Coffman is pursuing her personal trainer certification in 2015.